In this Temasek Young Investigator Award winning project funded by the DSTA, we aim to develop a fully functional UAV (unmanned aerial vehicle) helicopter system, named HeLion, which is shown in Figure 1. It consists of a small-scale basic helicopter with all the necessary accessories onboard and a ground station served by a laptop. The basic helicopter is about 1.41m in length and weighs 4.85kg. An embedded computer system is attached at the lower part of the UAV. The onboard system is composed of a PC/104 computer, an inertial measurement unit (IMU), a data acquisition board, a sonar chip, a wireless communication board, a set of servo drivers, and other necessary components.

HeLion is an excellent test bed for testing and implementing advanced linear and nonlinear control techniques. It is a very challenging process. The aerodynamics of small scale helicopters is similar to its full scale counterpart but has some unique characteristics of its own, such as the utilization of a stabilizer bar and higher main/tail rotor's rotation speed. Besides these differences, the strict limitation on payload also increases the difficulty of upgrading a small scale helicopter to a UAV with full capacities. Based on various characteristics and limitations of a small scale UAV helicopter, a light-weight but effective onboard computer system with corresponding onboard/ground software should be carefully designed to realize the system identification and automatic flight requirements. We have so far obtained a complete model of the dynamics of the UAV helicopter, and implemented an automatic flight control system design for hovering and circling test flights using a newly developed composite nonlinear feedback control mechanism, which has the capacity of yielding a fast transient response with minimal overshoot. Figure 2 is a picture showing the HeLion in action as it flies in an open field in Bukit Batok. We are currently investigating issues of full-envelope flights and ground target tracking and attacking.